Removal of arsenic(III) and arsenic(V) from sulfuric acid solution by liquid-liquid extraction

Extraction of arsenic(III) and arsenic(V) from sulfuric acid solution was studied. Cyanex((R)) 923, Cyanex((R)) 925, dialkyldithiophosphinic acids (Cyanex((R)) 301), hydrophobic glycol (2-ethylhexane-1,3-diol), and hydroxamic acids were used as extractants. The efficiency of extraction depended on extractant, diluent, valency of arsenic, and sulfuric acid concentration. Acidic reagents extracted As(III) better than As (V), while the opposite order of extraction efficiency was observed for the solvating extractants. The use of an aromatic diluent (toluene) was preferred. Toluene was found to be a better diluent for the Cyanex((R)) 923 and Cyanex((R)) 925 than Exxsol D 220/230 and octane. In the case of neo-decanohydroxamic acids, the type of diluent had no significant effect on extraction of arsenic. The extraction of both As(III) and As(V) increased when the concentration of the sulfuric acid in the feed increased. The co-extraction of sulfuric acid was observed. The extraction with hydroxamic acids was significantly slower in comparison to the extraction with other reagents. Extractant: arsenic species: sulfuric acid molar ratios were determined and they confirmed the composition of extracted species. (C) 2003 Society of Chemical Industry.